The human ankle comprises a great number of interconnected bones, muscles, ligaments, tendons and cartilage. This complex combination results in a joint capable of flexing in a wide range of directions. The movements are divided into four types: dorsiflexion, toward the position perpendicular to the leg; plantar flexion, toward the position extending away from the leg; inversion, toward the midline of the body; and eversion, away from the midline of the body.
The complexity and wide range of movement required of the ankle combined with the fact that the entire weight of the body is supported by the ankle results in the application of severe stresses. If an ankle is weak the application of a severe stress may cause injury. Injuries are most commonly caused by the ankle being forced to absorb a stress while flexed laterally or medially. Coming down on the side of one's foot while running or jumping is a typical example. The resultant sprained ankle must be immobilized for a period of weeks to heal, during which time the muscles of the lower leg experience atrophy. Therapy consisting of strengthening the lower leg muscles is required to reduce the possibility of reinjury and restore full use of the ankle.
The condition known as weak arches, or flat feet, is often accompanied by inadequate musculature in the lower leg. Weakness is this area makes a person more susceptible to both foot and ankle injuries. Strengthening these muscles increases the support provided by the foot and ankle and thereby increases resistance to injury.
Shin splints is a general term for injuries that result in a tearing of the tendons, muscles or interosseous membrane of the lower leg.
One cause of shin splints may be an imbalance between the calf muscles and anterior muscles. In a conditioning program the calf muscles may become stronger than the anterior muscles which may cause the tearing of the anterior muscles by the calf muscles.
Another possible cause of shin splints may be a weak arch. When the muscles of the foot become weak, the bones may spread resulting in a flattening of the arch. When this happens, the ligaments which secure the tendons of the muscles to the bones of the foot are loosened. This leads to the tendons lifting and pulling away from the bone.
Running on hard surfaces may cause another type of shin splint injury. An impact on the heel bone is transferred to the lower leg, whereupon, the two bones of the lower leg, the tibia and fibula, may be spread apart if the lower leg muscles are weak. This results in a tearing of the intersseous membrane that holds the tibia and fibula together.
All of the above injuries occur when the muscles of the lower leg and/or foot are weak or lack flexibility. An excellent way to prevent injuries such as ankle sprains and shin-splints from occurring as well as the quickest way to re-strengthen the ankle after it has recovered from an injury is to exercise the ankle by applying a resistance to the movement of the foot and ankle in a particular direction and then flexing the muscles of the ankle and lower leg against this. To maintain the muscular balance of the foot all of the muscles should be exercised. A complete series of exercises would include dorsiflexion, plantarflexion, inversion and eversion movements. The exercises should include a range of motion equivalent to that of a healthy ankle. Exercises involving the full range of motion have been shown to enhance flexibility and so further aid in injury prevention.
Doctors, physical therapists and athletic trainers suggest a variety of different exercises to strengthen the lower leg and ankle muscles. Most of these exercises are of an isometric nature, the muscle flexion being resisted by an immovable object or by an opposing muscle group so that the ankle does not move. This absence of motion is desirable when rehabilitating a recently injured ankle which must remain immobile for proper healing, but it is not necessary when trying to strengthen a healthy ankle. Isometric exercises are difficult to perform in that a great amount of mental discipline is required of the exerciser to perform a series of fullstrength muscle contractions which must be maintained for a period of 10 seconds or more. Isometric exercises do not provide the full range of motion that is required to improve flexibility.
Various devices have been designed to resist ankle flexion through a range of motion. However, most of these devices can provide resistance to movement in only one direction or, if they can resist several directions of movement, are cumbersome to use and difficult to adjust to the direction or level of resistance desired. Most prior art devices lack adequate range of motion for enhancing flexibility or stretching exercises.
The present invention is directed to providing an exercise device for strenghtening and rehabilitating the ankle and lower leg that overcomes the problems as set forth above.